The present application relates to a bidirectional optical communication module that encompasses a bidirectional optical communication chip for performing bidirectional optical communication using an optical fiber as an optical transmission path.
As broadband has become widely available in recent years, optical fibers serving as optical transmission paths are being introduced to ordinary households, and an optical network of subscribers to, for example, Fiber-To-The-Home (FTTH) that realizes high-speed communication is becoming realized. With regard to a transmission method used in such an optical network of subscribers, a bidirectional transmission method that performs transmission and reception using a single optical fiber is employed for achieving cost reduction.
In a bidirectional optical communication system terminal installed at the subscriber side (such as an ordinary household) based on the bidirectional transmission method, operation is performed for receiving reception signal light propagated through an optical transmission path and for transmitting transmission signal light toward the outside via the optical transmission path. As main components that fulfill this function, a light emitting element (e.g., a laser diode) that emits the transmission signal light and a light receiving element (e.g., a photodiode) that receives the reception signal light are used. In many cases, the bidirectional optical communication system terminal installed at the subscriber side includes a bidirectional optical communication module that contains the light emitting element and the light receiving element.
It is demanded that the bidirectional optical communication module have a function for efficiently guiding the transmission signal light from the light emitting element to the optical fiber serving as the optical transmission path and for efficiently guiding the reception signal light from the optical fiber to the light receiving element. The bidirectional optical communication system terminal needs to be reduced in size to an extent that the installation location does not require a very large space when the subscriber installs this terminal.
JP H10-206678A discloses an optical semiconductor element module as an example of a bidirectional optical communication module. The optical semiconductor element module includes a semiconductor laser constituting a transmitting section and a photodiode constituting a receiving section that are contained in separate packages, and further includes a band-pass filter that functions as a wavelength-division multiplexing (WDM) filter that divides the reception signal light and the transmission signal light from each other. These packages and the band-pass filter together constitute the optical semiconductor element module. Furthermore, JP H11-68705A attempts to reduce the size of a bidirectional optical communication module and the manufacturing costs thereof by integrating a semiconductor laser, a photodiode, and a WDM filter (dielectric multilayer filter) on an optical circuit board (silicon (Si) substrate).